Paved surfaces such as roads and parking lots are commonly constructed with a top surface layer of asphalt paving material. Over a period of time, the paved surface usually deteriorates due to the effects of traffic, temperature cycles and other environmental causes. Cracks develop in the paved surface, and the cracks can spread and cause further deterioration. Water can penetrate the paved surface by flowing into the cracks, causing further damage.
Damaged paved surfaces are usually repaired by applying a new surface layer of paving material over the damaged portions or over the entire paved surface. After a paved surface having cracks is resurfaced, many times the new surface layer cracks directly over the cracks in the old surface. This is known as “reflective cracking”. One way to address this problem is to make the new surface layer thicker, but this is not very effective.
Consequently, various materials and methods have been tried for waterproofing and for preventing or repairing cracks and other deterioration in paved surfaces. One commercial product (an example of which is Petromat® from BP Amoco) is a reinforcement mat constructed from nonwoven needle-punched polypropylene fibers. The polypropylene mat is applied over a tack coat of asphalt, and then a surface layer of paving material is applied over the mat. The paving material is heated prior to its application over the mat. Unfortunately, the polypropylene mat tends to melt and/or shrink when it is exposed to the hot paving material, which detracts from its ability to provide reinforcement and waterproofing. Additionally, if the tack coat is applied at too high a temperature, the polypropylene mat may likewise shrink or melt. Another commercial product is Mirapave 400®, a nonwoven heat-set polypropylene geotextile from Mirafi.
Some patents describe reinforcement materials and methods of reinforcing paved surfaces. For example, U.S. Pat. No. 2,115,667 to Ellis discloses reinforcing an asphalt road with a reinforcing agent made from woven glass. A woven reinforcement material is usually less porous than a nonwoven material. This impedes the ability of the asphalt to penetrate the reinforcement material to create a strong paved surface. A woven material is also usually more expensive to manufacture than a nonwoven material.
U.S. Pat. No. 6,235,136 to Kittson et al. discloses a water-resistant mastic membrane. The membrane comprises a carrier layer and a grid of glass fibers, both embedded in molten mastic material. The carrier layer is designed to provide only limited performance to the mastic membrane, and can be destroyed, or melted, by the molten mastic material. The membrane is bulky, having a thickness of 50 mm to 150 mm, and consists primarily of mastic material.